<!doctype html>
<meta charset="utf-8">
<title>CSS test reference.</title>
<style>
  .container div {
    width: 50px;
    height: 50px;
    background: blue;
  }
  .container div:nth-child(2) {
    background: green;
  }
</style>
<div class="container">
  <div></div>
  <div></div>
</div>
